The Pennsylvania Department of Environmental Protection (PADEP) has published draft guidance under 25 PA. Code Ch. 245-Storage Tank Regulations, to assist aboveground storage tank (AST) owners and professional engineers with determining the permeability and adequacy of emergency secondary containment structures.

Emergency containment is defined as a containment structure that will convey, capture, and contain the total volume of an anticipated release of regulated substance from an AST, or underground storage tank (UST) system, and is expeditiously emptied.

Both Large ASTs, with a capacity of greater than 21,000 gallons, and ASTs in underground vaults, require containment structures that are compatible with the substances stored in them while minimizing deterioration to the storage tank system. Additionally, emergency containment areas must have the capacity to contain 110% of the largest tank's capacity in that containment area.

New emergency containment structures, installed after October 11, 1997, must have a permeability of less than 1 x 10-6 cm/sec at anticipated hydrostatic head, and sufficient thickness to prevent the released substance from penetrating the containment structure for a minimum of 72 hours.

Emergency containment structures installed on or before October 11, 1997, must meet the standards for new emergency containment structures, or need to be verified by a Professional Engineer (PE). The PE will determine if the containment structure, coupled with the tank monitoring program and response plan, is capable of detecting and recovering a release and preventing contamination of the waters of the Commonwealth.

Emergency containment structures should be evaluated periodically and include the following determinations, testing and procedures, if applicable:

  • Determination of emergency containment permeability by a qualified industry professional Permeability testing
  • Restoration of the containment structure after testing
  • Verification of containment adequacy by a PE
  • Inspection of containment areas by DEP-certified AST inspector

Small ASTs, with a capacity of equal to or less than 21,000 gallons, have similar, simplified requirements.

Test methods used for evaluating emergency containment and general information on the various types of emergency containment are summarized in Appendices of the draft guidance document.

You can refer to the Verification of Emergency Containment Structures for Aboveground Storage Tanks guidance document, to read further about the detailed requirements of structure verification. Comments for the guidance document can be submitted until September 9, 2019.

For additional assistance, please contact Christie Heath, Manager of Trinity's Philadelphia office, at or call (610) 280-3902; or contact Ian Donaldson, Manager of Trinity's Pittsburgh office, at or call (724) 935-2611.